1. Field of the Invention
This invention relates to copper and copper alloy etching solutions and an etching process using said solutions. More particularly, it is concerned with copper and copper alloy etching solutions containing catalysts for greatly increasing the rate of etching.
2. Description of the Prior Art
Etching of copper and copper alloys is widely used in various industrial fields.
Particularly with development of the electronic industry, it has been technologically adopted in the production of printed circuit boards and lead frame of the IC circuit, and thereby acquired a greater importance.
Etching of copper and copper alloys has been performed using ferric chloride, cupric chloride, chromic-sulfuric acid mixtures, peroxysulfates and the like. Among them, use of chromic anhydride-sulfuric acid mixtures produces a waste containing dissolved copper and chromium and use of ferric chloride a waste containing a large amount of metallic copper and iron ions. Simultaneous and complete removal of these metals is so difficult that the process producing such a waste is unsuitable for use owing to the resulting pollution problem.
On the other hand, use of a peroxysulfate solution, which produces a waste containing copper only, is preferable as the etching solution because of the relative ease in removal of the copper. However, as the rate of etching copper and copper alloys is very slow with a persulfate alone, a catalyst should be added in order to achieve a rate of etching approximately equal to the rate usually achieved with ferric chloride. As described in Japanese Patent Publication 16008/1961, mercury salts are usually used as the catalyst. The waste from the etching is then contaminated with mercury ions, which, being very hazardous to living bodies, should be removed. However, as the complete removal of mercury is very difficult, development of substitute catalysts is eagerly desired.